PROJECT SUMMARY The purpose of this research is to transform the way we study social determinants of health in children. To date, efforts to understand how social experiences ?get under the skin? in childhood and adolescence have relied on biomarkers (e.g., cortisol, blood pressure, systemic inflammation) that have uncertain health significance during this developmental period when nearly all youth have values that reflect normative functioning. I propose to examine how chronic and acute stress exposure is linked to children's antibody response to vaccination?a measure that can be considered an in vivo marker of immune function with real clinical health relevance. This proposal focuses on children's responses to influenza vaccination, which is of particular importance because millions of children in the United States get the flu each year, and thousands are hospitalized due to complications. Further, although influenza vaccination reduces the risk of infection by about 50-60%, some individuals will not have a sufficient antibody response and will be at risk for infection despite vaccination. Research with adult samples has shown that some stressful experiences are associated with lower production of antibodies following vaccination. To date, however, no studies have explored connections between stress and antibody production following vaccination in children. By studying antibody production following vaccination, we can examine a health outcome in youth with clinical relevance. I will apply this methodological innovation in several studies. First, I will conduct innovative research aimed at understanding what kinds of chronic and acute stressors in childhood are most likely to be linked to children's antibody responses following vaccination. Then, I will consider dyadic-level effects by examining parents' and youths' stressful experiences and antibody responses, which will allow for analysis of how parents' psychosocial stress might affect children's antibody responses, and in turn how children's ongoing stressors are associated with parents' response to vaccination. After I gain insights into the links between psychosocial stress and antibody production within community samples, I propose to capitalize on an ongoing longitudinal study of rural African Americans that has followed families for over 15 years. These participants joined the study at age 11 and are currently in their late 20s. This unique sample is extremely well characterized, with annual assessments of exposure to socioeconomic disadvantage, parental depression and substance use, and coping strategies, as well as access to possible buffers (e.g., close friendships, self-regulatory capacities, community mentors), all of which may be associated with young adults' antibody production following vaccination. This study will allow us to examine whether experiences in childhood and adolescence influence vaccine responses in young adulthood. The current proposal has important public health implications by shedding light on risk factors in childhood and adolescence that might put certain individuals at risk for increased susceptibility to infection despite vaccination.